The present invention relates to the field of semiconductor assembly and packaging, and more particularly, to a molding press (and a platen thereof) for applying an encapsulant to semiconductor dies on a substrate.
Packaging, also known as encapsulation, is an important part of the semiconductor assembly process. Typically, encapsulation is performed by either transfer molding or compression molding.
In transfer molding, the molding system includes a first platen having a supply pot which receives a molding compound, for example in the form of a solid pellet. The first platen also has a plurality of cavities. The first platen is pressed against a second platen on which a substrate carrying a plurality of semiconductor dies is held, such that the cavities of the first platen overlie the semiconductor dies. The molding compound is melted, with the application of heat and pressure, to a liquid state, and the liquefied molding compound is then forced by a plunger into runners connected between the plunger and the molding cavities to enter into the molding cavities via narrow gates. The molding compound is then cured and the encapsulated substrate then removed from the mold.
In compression molding, a molding compound in the form of powder or liquid or paste resin is loaded into one or more mold cavities of a bottom platen (in the case of die-down molding) or directly onto a substrate which is held on the bottom platen (in the case of die-up molding). A heater plate in the bottom platen is then used to melt the molding compound. Next, a mold chase of a top platen is clamped against a mold chase of the bottom platen to form a mold cavity between the top and bottom platens, with the molten molding compound then being cured to form a mold cap which encapsulates the dies.
In either a transfer molding or a compression molding encapsulation process, it is critical to maintain substantial parallelism between the substrate and the opposed surface of the mold cavity. Otherwise, there may be defects in the mold cap caused by incomplete filling of the mold cavity.
There remains a need for a molding press which overcomes or alleviates at least one of the foregoing difficulties, or which at least provides a useful alternative.